Devices and methods for percutaneous surgery

ABSTRACT

Devices and methods for performing percutaneous spinal surgery under direct visualization and through a single cannula are shown. A device ( 10 ) is provided which includes an elongated cannula ( 20 ) having a first inner diameter (D I ) and an outer diameter (D O ) sized for percutaneous introduction into a patient. The cannula ( 20 ) defines a working channel ( 25 ) between its ends ( 21, 22 ) which has a second diameter (D 2 ) equal to the diameter (D I ) of the cannula sized for receiving a tool therethrough. An elongated viewing element ( 50 ) is engageable to the cannula ( 20 ) adjacent the working channel ( 25 ), preferably by a fixture ( 30 ). The fixture ( 30 ) includes a housing ( 31 ) attachable to the proximal end ( 22 ) of the cannula ( 20 ) that defines a working channel opening ( 35 ) which is in communication with the working channel ( 25 ). The housing ( 31 ) also defines an optics bore ( 60 ) adjacent the working channel opening ( 35 ). In certain embodiments, the fixture ( 30 ) supports the viewing element ( 50 ) for translation and/or rotation within the optics bore ( 60 ) along the longitudinal axis of the bore, and for rotation of the housing ( 31 ) relative to the cannula ( 20 ) so that the longitudinal axis of the optics bore ( 60 ) will rotate about the longitudinal axis of the working channel ( 25 ). Methods are also provided for performing spinal surgeries percutaneously with direct visualization and without the requirement for a fluid-maintained workspace.

This application is a divisional of pending U.S. patent application Ser.No. 08/920,990 filed on Aug. 29, 1997 now U.S. Pat. No. 5,954,635, whichis a divisional of U.S. patent application Ser. No. 08/620,933, filedMar. 22, 1996, now U.S. Pat. No. 5,792,044.

FIELD OF THE INVENTION

The present invention relates to devices, instruments and methods forperforming percutaneous surgeries, particularly at locations deep withinthe body. One specific application of the invention concern devices,instruments and techniques for percutaneous, minimally invasive spinalsurgery. In another aspect of the invention, the percutaneous surgery isperformed under direct vision at any location in the body.

BACKGROUND OF THE INVENTION

Traditional surgical procedures for pathologies located deep within thebody can cause significant trauma to the intervening tissues. These openprocedures often require a long incision, extensive muscle stripping,prolonged retraction of tissues, denervation and devascularization oftissue. Most of these surgeries require a recovery room time of severalhours and several weeks of post-operative recovery time due to the useof general anesthesia and the destruction of tissue during the surgicalprocedure. In some cases, these invasive procedures lead to permanentscarring and pain that can be more severe than the pain leading to thesurgical intervention.

Minimally invasive alternatives such as arthroscopic techniques reducepain, post-operative recovery time and the destruction of healthytissue. Orthopedic surgical patients have particularly benefitted fromminimally invasive surgical techniques. The site of pathology isaccessed through portals rather than through a significant incision thuspreserving the integrity of the intervening tissues. These minimallyinvasive techniques also often require only local anesthesia. Theavoidance of general anesthesia reduces post-operative recovery time andthe risk of complications.

Minimally invasive surgical techniques are particularly desirable forspinal and neurosurgical applications because of the need for access tolocations deep within the body and the danger of damage to vitalintervening tissues. For example, a common open procedure for discherniation, laminectomy followed by discectomy requires stripping ordissection of the major muscles of the back to expose the spine. In aposterior approach, tissue including spinal nerves and blood vesselsaround the dural sac, ligaments and muscle must be retracted to clear achannel from the skin to the disc. These procedures normally take atleast one-two hours to perform under general anesthesia and requirepost-operative recovery periods of at least several weeks. In additionto the long recovery time, the destruction of tissue is a majordisadvantage of open spinal procedures. This aspect of open proceduresis even more invasive when the discectomy is accompanied by fusion ofthe adjacent vertebrae. Many patients are reluctant to seek surgery as asolution to pain caused by herniated discs and other spinal conditionsbecause of the severe pain sometimes associated with the muscledissection.

In order to reduce the post-operative recovery time and pain associatedwith spinal and other procedures, micro-surgical techniques have beendeveloped. For example, in micro-surgical discectomies, the disc isaccessed by cutting a channel from the surface of the patient's back tothe disc through a small incision. An operating microscope or loupes isused to visualize the surgical field. Small diameter micro-surgicalinstruments are passed through the small incision and between twolaminae and into the disc. The intervening tissues are disrupted lessbecause the incision is smaller. Although these micro-surgicalprocedures are less invasive, they still involve some of the samecomplications associated with open procedures, such as injury to thenerve root and dural sac, perineural scar formation, reherniation at thesurgical site and instability due to excess bone removal.

Other attempts have been made for minimally invasive procedures tocorrect symptomatic spinal conditions. One example is chemonucleolysiswhich involved the injection of an enzyme into the disc to partiallydissolve the nucleus to alleviate disc herniation. Unfortunately, theenzyme, chymopapain, has been plagued by concerns about both itseffectiveness and complications such as severe spasms, post-operativepain and sensitivity reactions including anaphylactic shock.

The development of percutaneous spinal procedures has yielded a majorimprovement in reducing recovery time and post-operative pain becausethey require minimal, if any, muscle dissection and they can beperformed under local anesthesia. For example, U.S. Pat. No. 4,545,374to Jacobson discloses a percutaneous lumbar discectomy using a lateralapproach, preferably under fluoroscopic X-ray. This procedure is limitedbecause it does not provide direct visualization of the discectomy site.

Other procedures have been developed which include arthroscopicvisualization of the spine and intervening structures. U.S. Pat. Nos.4,573,448 and 5,395,317 to Kambin disclose percutaneous decompression ofherniated discs with a posterolateral approach. Fragments of theherniated disc are evacuated through a cannula positioned against theannulus. The '317 Xambin patent discloses a biportal procedure whichinvolves percutaneously placing both a working cannula and avisualization cannula for an endoscope. This procedure allowssimultaneous visualization and suction, irrigation and resection in discprocedures.

Unfortunately, disadvantages remain with these procedures and theaccompanying tools because they are limited to a specific application orapproach. For example, Jacobson, Kambin and other references require alateral or a posterolateral approach for percutaneous discectomy. Theseapproaches seek to avoid damage to soft tissue structures and the needfor bone removal because it was thought to be impractical to cut andremove bone through a channel. However, these approaches do not addressother spinal conditions which may require a mid-line approach, removalof bone or implants.

U.S. Pat. No. 5,439,464 to Shapiro discloses a method and instrumentsfor performing arthroscopic spinal surgeries such as laminectomies andfusions with a mid-line or medial posterior approach using threecannulas. Each of the cannulas requires a separate incision. WhileShapiro discloses an improvement over prior procedures which werelimited to a posterolateral or lateral approach for disc work, Shapiro'sprocedure still suffers from many of the disadvantages of known priorpercutaneous spinal surgery techniques and tools. One disadvantage ofthe Shapiro procedure is its requirement of a fluid working space.Another significant detriment is that the procedure requires multipleportals into the patient.

Fluid is required in these prior procedures to maintain the workingspace for proper function of optics fixed within a prior art cannula andinserted percutaneously. Irrigation, or the introduction of fluid intothe working space, can often be logistically disadvantageous and evendangerous to the patient for several reasons. The introduction of fluidinto the working space makes hemostasis more difficult and may damagesurrounding tissue. Excess fluid may dangerously dilute the sodiumconcentration of the patient's blood supply which can cause seizures orworse. The fluid environment can also make drilling difficult due tocavitation. The requirement for a fluid environment generally increasesexpenses associated with the surgery and adds to the complexity of thesurgery, due in part to the relatively high volume of fluid required.

A need has remained for devices and methods that provide forpercutaneous minimally invasive surgery for all applications andapproaches. A need has also remained for percutaneous methods anddevices which do not require a fluid-filled working space, but that canbe adapted to a fluid environment if necessary.

A signficant need is present in this field for techniques andinstruments that permit surgical procedures in the working space underdirect vision. Procedures that reduce the number of entries into thepatient are also highly desirable. The fields of spinal and neurosurgery have particularly sought devices and techniques that minimizethe invasion into the patient and that are streamlined and concise intheir application.

SUMMARY OF THE INVENTION

Briefly describing one aspect of the invention, there is provideddevices and method for performing percutaneous procedures under directvisualization, even at locations deep within a patient. In oneembodiment, a device for use in percutaneous surgery includes anelongated cannula having a first inner diameter and an outer diametersized for percutaneous introduction into a patient. The cannula furtherincludes a distal working end and an opposite proximal end and defines aworking channel between the ends having a second diameter which is equalto the first inner diameter. The working channel is sized to receive atool therethrough. The device also includes an elongated viewing elementmounted inside the cannula adjacent the working channel. The viewingelement has a first end connectable to a viewing apparatus and anopposite second end disposed adjacent the distal working end of thecannula.

In another aspect, a fixture is provided for mounting the elongatedviewing element to the cannula. The fixture includes a housingattachable to the proximal end of the cannula. The housing defines aworking channel opening therethrough in communication with the workingchannel. The working channel opening is sized to substantiallycorrespond to the second diameter of the working channel. The housingalso defines an optics bore adjacent the working channel opening. Theoptics bore is sized to receive the elongated viewing elementtherethrough.

In some embodiments, the fixture supports the viewing device formovement within the optics bore along the longitudinal axis of the boreto extend or retract the lens relative to the distal working end of thecannula. In other embodiments, the fixture supports the viewing devicefor rotation within the optics bore about the longitudinal axis of thebore. In some embodiments, the housing is rotatable relative to thecannula so that the longitudinal axis of the optics bore is rotatableabout the longitudinal axis of the working channel.

Novel tools are also provided which are insertable into the workingchannel of the cannula. A tissue retractor in one embodiment includes abody and an integral working tip configured to atraumatically displacetissue as the retractor is manipulated through tissue. The body has aconvex surface configured to conform to the inner cylindrical surface ofthe cannula and an opposite concave surface which does not obstruct theworking channel or visualization of the working space. Cannulated tissuedilators are also provided which are insertable over a guidewire oranother dilator as well as insertable into the working channel. In someembodiments, the tissue dilators include a tapered working end todisplace tissue and a gripping portion having a number ofcircumferential grooves to enhance gripping and manipulation of thedilator.

According to the methods of this invention, spinal and other surgeriescan be performed percutaneously with direct visualization without therequirement for a fluid-maintained working space. In another aspect ofthe inventive surgical techniques, all steps of a surgical procedure areconducted under direct vision through a single working channel cannula.An optical scope or viewing device is moved within the working channeland throughout the working space from a variety of angles andorientations to provide a clear view of the operative steps.

The techniques of the present invention also encompass passing multipletools and instruments through the single working channel cannula andmanipulating the instruments and tools within the working space. In onespecific embodiment, a tissue retractor is provided that extends throughthe working channel without significantly reducing the dimensions of thechannel.

It is an object of the invention to provide devices and methods forpercutaneous spinal surgery for all applications and approaches. Oneadvantage of this invention is that percutaneous procedures can beaccomplished in a dry environment because a fluid working space is notrequired for the proper function of the optics. One benefit of thisinvention is that it provides instruments and methods which reduce thecost, risk, pain and recovery time associated with surgery. These andother objects, advantages and features are accomplished according to thedevices and methods of the present invention.

DESCRIPTION OF THE FIGURES

FIG. 1 is a side elevational view of a device according to thisinvention.

FIG. 2 is a top elevational view of a fixture for supporting a viewingdevice within a cannula according to this invention.

FIG. 3 is a side cross-sectional view of the fixture shown in FIG. 2.

FIG. 4 is a side elevational view of a retractor according to oneembodiment of this invention.

FIG. 4A is an end cross-sectional view of the retractor of FIG. 4 takenalong lines A—A.

FIG. 5 is a top elevational view of the retractor shown in FIG. 4.

FIG. 6 is an end elevational view of the retractor shown in FIGS. 4 and5.

FIG. 7 is a side elevational view of a retractor according to anotherembodiment of this invention.

FIG. 7A is an end cross-sectional view of the retractor of FIG. 7 takenalong lines A—A.

FIG. 7B is an end cross-sectional view of the retractor of FIG. 7 takenalong lines B—B.

FIG. 8 is a top elevational view of the retractor shown in FIG. 7.

FIG. 9 is a side elevational view of a dilator according to thisinvention.

FIGS. 10 (a)-(i) depicts the steps of a method according to thisinvention.

FIG. 11 is a side cross-sectional view of a device according to oneembodiment of this invention.

FIG. 12 is a side cross-sectional view of an aspiration cap as shown inFIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated devices and described methods, and suchfurther applications of the principles of the invention as illustratedtherein being contemplated as would normally occur to one skilled in theart to which the invention relates.

The present invention provides instruments and methods for performingpercutaneous surgery, including spinal applications such as laminotomy,laminectomy, foramenotomy, facetectomy or discectomy, with a singleworking channel endoscope. The present inventors have discovered thatmany percutaneous surgeries may be performed without a fluid workspacethrough the use of optics which move independently of the cannula. Thepresent invention contemplates techniques and instruments that can beimplemented with or without a fluid environment.

This invention also brings the advantages of percutaneous procedures toapplications that previously required open surgery. One advantage isbased upon the further discovery that bone work can be performedpercutaneously through a large working channel. Another advantage isrealized in the use of a single portal within the patient to perform awide range of simultaneous procedures.

According to one embodiment of the present invention, as depicted inFIG. 1, a device 10 is provided for use in percutaneous surgery whichincludes an elongated cannula 20 having a first inner diameter D_(I) andan outer diameter D_(O) sized for percutaneous introduction into apatient. The cannula 20 also includes a distal working end 21 and anopposite proximal end 22. The cannula defines a working channel 25between the ends 21, 22 having a second diameter d₂ equal to the firstinner diameter D_(I) sized for receiving a tool therethrough. Thecannula has a length along its longitudinal axis L that is sized to passthrough the patient from the skin to an operative site or working space.In some cases, the working space may be adjacent a vertebra or disc, orin the spinal canal.

An elongated viewing element 50 is mountable inside cannula 20 adjacentthe working channel 25. The viewing element 50 has a first end 51connectable to a viewing apparatus, such as an eyepiece or camera, andan opposite second end 52 disposed or positionable adjacent the distalworking end 21 of the cannula 20. The particular elongated viewingelement 50 is not critical to the invention. Any suitable viewingelement is contemplated that creates an optical or image transmissionchannel. In one embodiment, the elongated viewing element 50 includes afiber optic scope 54 and a lens 55 at the second end 52. Preferably, thefiber optic scope includes illumination fibers and image transmissionfibers (not shown). Alternatively, the viewing element may be a rigidendoscope or an endoscope having a steerable or bendable tip.

One advantage of this invention is that it provides optics which aremovable relative to the cannula 20. Because the optics are movable, itis not necessary to provide a fluid-maintained work space. The opticscan be removed, cleaned and replaced while the cannula is percutaneouslypositioned within the patient over the working space. Any configurationwhich allows the optics to be movably supported adjacent the workingchannel 25 is contemplated. In one embodiment, shown in FIGS. 1-3, afixture 30 is provided for mounting the elongated viewing element 50 tothe cannula 20. Preferably, the fixture 30 includes a housing 31attachable to the proximal end 22 of the cannula 20. The working channelopening 35 is sized to substantially correspond to the second diameterd₂ of the working channel 25 to receive tools. The fixture 30 includes ahousing 31 which defines a working channel opening 35 arranged tocommunicate with the working channel 25 when the fixture 30 is mountedto the cannula 20. The working channel opening 35 is sized to receivetools therethrough for passage through the working channel 25. In theembodiments shown in FIGS. 1-3, the fixture 30 is configured to mountthe viewing element 50 within the Working channel 25.

The housing 31 also defines an optics bore 60 adjacent the workingchannel opening 35. The optics bore 60 has a longitudinal axis l that ispreferably substantially parallel to the axis L of the cannula an dworking channel. The optics bore 60 is preferably sized to removablyreceive the elongated viewing element 50 therethrough. The fixture 30preferably supports the viewing element 50 for movement within theoptics bore 60 along the longitudinal axis l of the bore 60 to extend orretract the lens 55 relative to the distal working end 21 of the cannula20. The retractable/extendable feature of the optics of this inventionprovides an advantage over prior endoscopes because it eliminates therequirement for a fluid workspace. While the device 10 and its viewingelement 50 can be easily used in a fluid environment, the fluid is notessential for the system to operate, contrary to prior systems.Furthermore, many of the prior endoscopes were not suited to accesscertain areas because of their large diameters. For example, priorendoscopes could not access the spinal canal. However, with thisinvention, access to the spinal canal is not limited by the diameter ofthe channel or cannula. The cannula 20 can be left behind in the softtissue or supported by the lamina while the second end 52 of theelongated viewing element 50 can be advanced into the spinal canal alongwith any spinal instruments which have been inserted into the workingchannel 25.

Preferably the fixture 30 also supports the viewing element 50 forrotation within the optics bore 60 about the longitudinal axis l of thebore 60. The lens 55 of the viewing element 50 defines an optical axisA_(O). As in many endoscopes, the optical axis A_(O) can be offset at anangle relative to the longitudinal axis l of the optics bore 60. Thisfeature allows the optical axis A_(O) of the lens to be swept through aconical field of view F for greater visibility of the working space. Thefixture 30 can further be configured so that the viewing element 50 isrotatable relative to the cannula 20. In this embodiment, the housing 31is rotatable relative to the cannula 20 so that the second longitudinalaxis l of the optics bore 60 rotates about the longitudinal axis L ofthe working channel 25. The rotatable features of this invention allowsvisualization of the entire working space. This feature also aids insimplifying the surgical procedure because the optics 50 andaccompanying fittings can be moved out of the way of the surgeon's handsand tools passing through the working channel.

In one embodiment depicted in FIG. 3, the housing 31 defines a receiverbore 40 having an inner diameter d_(I) slightly larger than the outerdiameter D_(O) of the cannula 20. In this configuration, the proximalend 22 of the cannula 20 can be received within the receiver bore 40 sothat the housing 31 can rotate about the proximal end 22 of the cannula20. As shown in FIG. 3, the housing 31 also includes an upper bore 41which is contiguous with the working channel opening 35 and the receiverbore 40. In one embodiment, the optics bore 60 is disposed within theupper bore 41 of the housing 31.

In a preferred embodiment depicted in FIG. 2, the optics bore 60 isdefined by a C-shaped clip 61 disposed within the upper bore 41.Preferably, the C-shaped clip 61 is formed of a resilient material andthe optics bore 60 defined by the clip 61 has an inner diameter D_(i)that is slightly less than the outer diameter of the elongated viewingelement 50. When the viewing element 50 is pushed into the optics bore60 it resiliently deflects the C-shaped clip 61. The resilience of theclip 61 provides a gripping force on the element 50 to hold it in thedesired position, while still allowing the element 50 to berepositioned.

Alternatively, the optics bore 60 can have an inner diameter larger thanthe outer diameter of the viewing element. In this instance, the viewingelement 50 can be supported outside the device 20, either manually or bya separate support fixture.

Preferably the device 10 provides engagement means for securely yetrotatably engaging the fixture 30 to the cannula 20. Most preferably,the fixture 30 is configured to engage a standard cannula 20. Engagementmeans can be disposed between the housing 31 and the cannula 20 when thefixture 30 is mounted to the proximal end 22 of the cannula 20 forproviding gripping engagement between the housing 31 and the cannula 20.In one embodiment depicted in FIG. 3 the engagement means includes anumber of grooves 32 within the receiver bore 40 and a resilient sealingmember, such as an O-ring (see FIG. 11) disposed in each groove 32. Thesealing members, or O-rings, disposed between the housing 31 and theouter diameter D_(O) of the cannula 20 rotatably secure the fixture 30to the cannula 20. The O-rings provide sufficient resistance to movementto hold the fixture 30 in a selectable position on the cannula. Inanother embodiment, the housing 31 defines a receiver bore 40 which hasan inner diameter d_(I) which is only slightly larger than the outerdiameter D_(O) of the cannula 20 so that the housing 31 can rotatefreely about the cannula 20.

The working channel 25 and the working channel opening 35 are both sizedto receive a tool or instrument therethrough. Preferably, the workingchannel opening 35 of the housing 31 has a diameter Dw which issubstantially equal to the inner diameter d₂ of the working channel 25so that the effective diameter of the working channel is not reduced bythe fixture 30. This configuration provides a maximum amount of spacefor the insertion of tools into the working channel 25. The presentinvention is advantageous because standard micro-surgical spinal toolscan be inserted into the working channel and manipulated to perform asurgical procedure. The present invention is particularly advantageousbecause the working channel 25 will simultaneously accept a plurality ofmovable instruments. No other known prior art device has a workingchannel that accepts more than one movable instrument at a time througha single port. Therefore, according to this invention, an entirepercutaneous surgical procedure can be performed through the workingchannel 25 of the device 10 under direct visualization using the viewingelement 50 disposed within the optics bore 60.

Although standard micro-surgical instruments may be used with thepresent invention, this invention also contemplates certain novel toolswhich capitalize on and enhance the advantages of this invention.

According to one preferred embodiment of the invention, a tissueretractor 70 is provided as depicted in FIGS. 4-6. The retractor 70 isremovably and rotatably insertable through the working channel 25 andthe working channel opening 35 of the device 10. The tissue retractor 70includes a working tip 75 configured to atraumatically displace tissueas the retractor 70 is manipulated through the tissue and a body 76having a proximal first end 77 and a distal second end 78. The secondend 78 can be integral with the working tip 75 which preferably has ablunt curved end 82. In addition, the working tip 75 is also preferablybent or curved away from the body 76, as shown in FIG. 7. The body 76 issized to be rotatably received within the cannula 20 and has a length Bfrom the first end 77 to the second end 78 sufficient so that the firstend 77 and the working tip 75 can both extend outside the cannula 20when the body 76 is within the cannula 20.

This invention contemplates any suitable retractor for use through theworking channel 25. However, retractors such as the retractor 70depicted in FIGS. 4-6 are preferred in which the body 76 includes acurved plate 84 that is configured to conform to the inner cylindricalsurface 26 of the cannula without substantially blocking the workingchannel 25. The curved plate 84 has a convex surface 60 and an oppositeconcave surface 81. In one embodiment, the curved plate 84 includes afirst plate portion 85 defining a first convex surface 80 and anopposite first concave surface 81. A second plate portion 86 is integralwith the first plate portion 85 and is disposed between the first plateportion 85 and the working tip 75. The second plate portion 86 defines asecond convex surface (not shown) and an opposite second concave surface81′. Both the first plate portion 85 and the second plate portion 86include opposite edges 90 extending substantially parallel to the lengthB of the body 76.

Preferably, the curved plate 84 subtends an arc A₁ between the oppositeedges 90 of at least 200 degrees, and most preferably 270 degrees. In aspecific embodiment, the second plate portion 86 and specifically thesecond concave surface 81′ subtends an angle that decreases along thelength of the retractor. Thus, in an embodiment, the second concavesurface 81′ subtends an angle of about 200 degrees adjacent the firstplate portion 85, decreasing to an angle of less than about 10 degreesat end 78.

An alternate embodiment of a tissue retractor according to thisinvention is depicted in FIGS. 7-8. This retractor 100 has a body 106which includes a first plate portion 115 defining a first convex surface110 and an opposite first concave surface 111 and includes firstopposite edges 120 extending substantially parallel to the length B ofthe body 106. The first plate portion 115 subtends a first arc A₂between the first opposite edges 120. The retractor body 106 alsoincludes a second plate portion 116 which is integral with the firstplate portion 115 and is disposed between the first plate portion 115and a working tip 105. The second plate portion 116 defines a secondconvex surface 110′ and an opposite second concave surface 111′ andincludes second opposite edges 120′ extending substantially parallel tothe length B. The second plate portion 116 subtends a second arc A₃between the second opposite edges 120′ that is different from the firstarc A₂ in this embodiment. Preferably, the first arc A₂ subtends anangle of less than 180 degrees and the second arc A₃ subtends an angleof more than 180 degrees. Most preferably, the first arc A₂ subtends anangle of about 90 degrees and the second arc A₃ subtends an angle ofabout 270 degrees.

The retractors of this invention may be provided with means for engagingthe retractors 70, 100 within the working channel 25 of the cannula 20.For example, the convex surfaces 80, 110 can be configured to have adiameter that is greater than the diameter D_(I) of the innercylindrical surface 26 of the cannula 20. In that case, the body 76, 106may be formed of a resilient material that is deformable to beinsertable into the cannula 20 so that the convex surface 80, 110 is incontact with the inner cylindrical surface 26 of the cannula 20. Whenthe body 76, 106 is deformed, it exerts an outward force against thesurface 26 to frictionally hold the retractor in its selected position.

The preferred components provided by this invention are configured sothat multiple tools and instruments can be accepted and manipulatedwithin the working channel 25 of the cannula 20. The components are alsoconfigured so that more than one surgeon may manipulate instrumentsthrough the working channel 25 of the cannula 20 at one time. Forexample, one surgeon may be manipulating the retractor while anothersurgeon is drilling into a bone. The curvature of the body 76, 106 ofthe retractors 70, 100 provides more working space and increasesvisibility. Another feature is that the long axis of the component canbe placed in the working channel 25 while a bend in the handle portionkeeps hands away from the channel 25 so that more than one surgeon canwork in the channel 25 and more tools can be placed in the channel 25.The retractors shown in FIGS. 4-8 each comprise an arm 71, 101 attachedto the proximal first end 77, 107 of the body 76, 106. Preferably, asshown in FIGS. 4-8, the arm 71, 101 is at an angle α which is less than180 degrees from the longitudinal axis of the length L of the body 76.Most preferably, the angle α is about 90 degrees so that the arm 71, 101is substantially perpendicular to the length L of the body 76, 106.Preferably, the arm 71, 101′has a gripping surface 72, 102 to facilitatemanipulation of the retractor 70, 100.

The present invention also provides tissue dilators usable with thedevice 10. Any dilator which is insertable into the working channel 25of the cannula 20 is contemplated; however, a preferred dilator providedby this invention is depicted in FIG. 9. A dilator 130 preferablyincludes a hollow sleeve 135 defining a channel 131. The channel 131allows the dilator 130 to be placed over a guidewire (not shown) orother dilators. The hollow sleeve 135 has a working end 136 defining afirst opening 132 in communication with the channel 131 and an oppositeend 137 defining a second opening 133. The working end 136 is tapered toa tapered tip 138 to atraumatically displace tissue. Preferably, agripping portion 140 is provided on the outer surface 141 of the sleeve135 adjacent the opposite end 137. In one embodiment, the grippingportion 140 is defined by a plurality of circumferential grooves 142defined in the outer surface 141. The grooves 142 are configured formanual gripping of the dilator 130 to manipulate the dilator 130 throughtissue. Preferably, the grooves 142 are partially cylindrical. In theembodiment shown in FIG. 9, the gripping portion 140 includes a numberof circumferential flats 143 each of the circumferential grooves 142.The grooves 142 have a first width W₁ along the length of the sleeve 135and the flats 143 have a second width W₂ 146 along the length.Preferably, the first and second widths W₁ and W₂ are substantiallyequal.

The present invention has application to a wide range of surgicalprocedures, and particularly spinal procedures such as laminotomy,laminectomy, foramenotomy, facetectomy and discectomy. Prior surgicaltechniques for each of these procedures has evolved from a grosslyinvasive open surgeries to the minimally invasive techniques representedby the patents of Kambin and Shapiro. However, in each of theseminimally invasive techniques, multiple entries into the patient isrequired. Moreover, most of the prior minimally invasive techniques arereadily adapted only for a posterolateral approach to the spine. Thedevices and instruments of the present invention have application in aninventive surgical technique that permits each of these several types ofsurgical procedures to be performed via a single working channel. Thisinvention can also be used from any approach and in other regionsbesides the spine.

The steps of a spinal surgical procedure in accordance with one aspectof the present invention are depicted in FIG. 10. As can be readily seenfrom each of the depicted steps (a)-(i), the present embodiment of theinvention permits a substantially mid-line or medial posterior approachto the spine. Of course, it is understood that many of the followingsurgical steps can be performed from other approaches to the spine, suchas posterolateral and anterior. In a first step of the technique, aguidewire 150 can be advanced through the skin and tissue into thelaminae M of a vertebral body V. Preferably, a small incision is made inthe skin to facilitate penetration of the guidewire through the skin. Inaddition, most preferably the guidewire, which may be a K-wire, isinserted under radiographic or image guided control to verify its properpositioning within the laminae L of the vertebra V. It is, of course,understood that the guidewire 150 can be positioned at virtually anylocation in the spine and in any portion of a vertebra V. Thepositioning of the guidewire is dependent upon the surgical procedure tobe conducted through the working channel cannula of the presentintention. Preferably, the guidewire 150 is solidly anchored into thevertebral bone, being tapped by a mallet if necessary.

In subsequent steps of the preferred method, a series of tissue dilatorsare advanced over the guidewire 150, as depicted in steps (b)-(d) inFIG. 10. Alternatively, the dilators can be advanced through theincision without the aid of a guidewire, followed by blunt dissection ofthe underlying tissues. In the specific illustrated embodiment, a seriesof successively larger dilators 151, 152 and 153 are concentricallydisposed over each other and over the guidewire 150 and advanced intothe body to sequentially dilate the perispinous soft tissues. Mostpreferably, the tissue dilators are of the type shown in FIG. 9 of thepresent application. In a specific embodiment, the dilators havesuccessively larger diameters, ranging from 5 mm, to 9 mm to 12.5 mm forthe largest dilator. Other dilator sizes are contemplated depending uponthe anatomical approach and upon the desired size of the workingchannel.

In the next step of the illustrated technique, the working channelcannula 20 is advanced over the largest dilator 153, as shown in step(e), and the dilators and guidewire 150 are removed, as shown in step(f). Preferably, the working channel cannula 20 has an inner diameterD_(I) of 12.7 mm so that it can be easily advanced over the 12.5 mmouter diameter of the large dilator 153. Larger working channel cannulasare contemplated depending upon the anatomical region and surgicalprocedure.

With the cannula 20 in position, a working channel is formed between theskin of the patient to a working space adjacent the spine. It isunderstood that the length of the cannula 20 is determined by theparticular surgical operation being performed and the anatomysurrounding the working space. For instance, in the lumbar spine thedistance between the laminae M of a vertebra V to the skin of thepatient requires a longer cannula 20 than a similar procedure performedin the cervical spine where the vertebral body is closer to the skin. Inone specific embodiment in which the cannula 20 is used in a lumbardiscectomy procedure, the cannula has a length of 87 mm, althoughgenerally only about half of the length of the cannula will be situatedwithin the patient during the procedure.

In accordance with the present surgical technique, the working channelcannula 20 is at least initially only supported by the soft tissue andskin of the patient. Thus, in one aspect of the preferred embodiment,the cannula 20 can include a mounting bracket 27 affixed to the outersurface of the cannula (FIG. 10(f), FIG. 11). This mounting bracket 27can be fastened to a flexible support arm 160, which can be of knowndesign. Preferably, the flexible support arm 160 is engaged the bracket27 by way of a bolt and wing nut 161, as shown in FIG. 10 (i) and inmore detail in FIG. 11, although other fasteners are also contemplated.This flexible arm 160 can be mounted on the surgical table and can bereadily adjusted into a fixed position to provide firm support for thecannula 20. The flexible arm 160 is preferred so that it can becontoured as required to stay clear of the surgical site and to allowthe surgeons adequate room to manipulate the variety of tools that:would be used throughout the procedure.

Returning to FIG. 10, once the cannula 20 is seated within the patient,the fixture 30 can be engaged over the proximal end of the cannula 20.The fixture 30, as shown in FIGS. 2 and 3 and as described above,provides an optics bore 60 for supporting an elongated viewing element,such as element 50 shown in step h. In accordance with the invention,the viewing element 50 is advanced into the fixture 30 and supported bythe optics bore 60 (FIG. 2). In one specific embodiment, the element 50is most preferably a fiber optic scope, although a rod lens scope orother viewing scopes may be utilized. In the final step (i) of theprocedure shown in FIG. 10, the flexible arm 160 is mounted to thebracket 27 to support the cannula 20 which in turn supports the opticalviewing element 50. This final position of step (i) in FIG. 10 is shownin more detail in FIG. 11. The viewing element 50 can be of a variety oftypes, including a rigid endoscope or a flexible and steerable scope.

With the viewing element or scope 50 supported by the fixture 30 thesurgeon can directly visualize the area beneath the working channel 25of the cannula 20. The surgeon can freely manipulate the viewing element50 within the working channel 25 or beyond the distal end of the cannulainto the working space. In the case of a steerable tip scope, the secondend 52 of the viewing element 50, which carries the lens 55, can bemanipulated to different positions, such as shown in FIG. 11. Withvirtually any type of viewing element, the manipulation and positioningof the scope is not limited by the working channel 25, in contrast toprior systems.

Preferably, the positioning capability provided by the fixture 30 isutilized to allow extension of the lens 55 into the working space orretraction back within the cannula 20, as depicted by the arrows T inFIG. 1. Also the fixture preferably accommodates rotation of the element50 about its own axis (arrows R in FIG. 1) to vary the viewing angleprovided by the angled lens 55, or rotation of the entire viewingelement 50 about the cannula 20 and around the circumference of theworking channel 25, as shown by the arrows N in FIG. 1. In this manner,the surgeon is provided with a complete and unrestricted view of theentire working space beneath the working channel 25. In instances whenthe fixture 30 is rotated about the cannula 20, the viewing orientationof the optics (i.e., left-right and up-down) is not altered so thesurgeon's view of the procedure and surrounding anatomy is notdisturbed.

Another advantage provided by the single working channel cannula 20 ofthe present invention, is that the cannula can be readily positionedover an appropriate target tissue or bone, to thereby move the workingspace as necessary for the surgical procedure. In other words, since theworking channel cannula 20 is freely situated within the patient's skinand tissue, it can be manipulated so that the working space beneath thecannula 20 is more appropriately centered over the target region of thespine. Repositioning of the cannula 20 can be performed underfluoroscopic guidance. Alternatively, the cannula may be fitted withposition sensing devices, such as LEDs, to be guided stereotactically.As the cannula is being repositioned, the surgeon can also directlyvisualize the spine through the viewing element 50.

Once the position of the cannula 20 is established and a working spaceis oriented over the proper target tissue, a variety of tools andinstruments can be extended through the working channel 25 to accomplishthe particular surgical procedure to be performed. For instance, in thecase of a laminotomy, laminectomy, foramenotomy or facetectomy, avariety of rongeurs, curettes, and trephines can be extended through theworking channel opening 35 (see FIG. 2) and through the working channel25 of the cannula 20 (see FIG. 11) into the working space. It isunderstood that these various tools and instruments are designed to fitthrough the working channel. For instance, in one specific embodiment,the working channel 25 through the cannula 20 can have a maximumdiameter d₂ of 12.7 mm. However, with the viewing element 50 extendinginto the working channel 25, the effective diameter is about 8 mm in thespecific illustrated embodiment, although adequate space is providedwithin the working channel 25 around the viewing element 50 to allow awide range of movement of the tool or instrument within the workingchannel. The present invention is not limited to particular sizes forthe working channel and effective diameter, since the dimensions of thecomponents will depend upon the anatomy of the surgical site and thetype of procedure being performed.

Preferably, each of the tools and instruments used with the workingchannel cannula 20 are designed to minimize obstruction of the surgeon'svisualization of and access to the working space at the distal end ofthe working channel cannula. Likewise, the instruments and tools aredesigned so that their actuating ends which are manipulated by thesurgeon are displaced from the working channel cannula 20. One suchexample is the tissue retractor shown in FIGS. 4-8. With theseretractors, the handles that are manually gripped by the surgeon areoffset at about a 90 degree angle relative to the longitudinal axis ofthe tool itself.

In accordance with once aspect of the present invention, the surgicalprocedures conducted through the working channel cannula 20 and withinthe working space at the distal end of the cannula are performed“dry”—that is, without the use of irrigation fluid. In prior surgicaltechniques, the working space at the surgical site is fluid filled tomaintain the working space and to assist in the use of the visualizationoptics. However, in these prior systems the visualization optics werefixed within the endoscope. In contrast, the device 10 of the presentinvention allows a wide range of movement for the viewing element 50 sothat the lens 55 can be retracted completely within the working channel25 of the cannula 20 to protect it from contact with the perispinoustissue or blood that may be generated at the surgical site.

Moreover, since the viewing element 50 is removable and replaceable, theelement 50 can be completely removed from the fixture 30 so that thelens 55 can be cleaned, after which the viewing element 50 can bereinserted into the fixture and advanced back to the working space.Under these circumstances, then, the need for irrigation is lesscritical. This feature can be of particular value when cuttingoperations are being performed by a power drill. It has been found inprior surgical procedures that the use of a power drill in a fluidenvironment can cause turbulence or cavitation of the fluid. Thisturbulence can completely shroud the surgeon's view of the surgical siteat least while the drill is being operated. With the present invention,the dry environment allows continuous viewing of the operation of thepower drill so that the surgeon can quickly and efficiently perform thenecessary cutting procedures.

While the present invention permits the surgeon to conduct surgicalprocedures in the working space under a dry environment, irrigation maybe provided separately through the working channel 25. Alternatively,the viewing device 50 itself may include a tube 54 supported by thefitting 53 through which modest amounts of fluid can be provided to keepthe visualization space clear. In addition, during a discectomy,aspiration of the excised tissue is preferred, and irrigation willfrequently assist in rapid removal of this tissue. Thus, separateirrigation and aspiration elements can also be inserted through theworking channel 25 as required by the procedure.

As necessary, aspiration can be conducted directly through the workingchannel 25 of the cannula 20. In one specific embodiment, an aspirationcap 165 is provided as shown in FIGS. 11 and 12. The cap 165 includes abody 166 which defines a mating bore 167 having an inner diameter d_(b)larger than the outer diameter D_(h) of the housing 31 of fitting 30. Atool opening 168 is provided in communication with the mating bore 167.When the aspiration cap 165 is mounted over the housing 31, as shown inFIG. 11, the tool opening 168 communicates directly with the upper bore41 and provides the same entry capabilities as the working channelopening 35 of the housing 31. The aspiration cap 165 is also providedwith a tube receiver bore 169 which intersects the mating bore 167. Thereceiver bore 169 is configured to receive an aspiration tube throughwhich a vacuum or suction is applied. In certain instances, the toolopening 168 may be covered while suction is applied, through the toolreceiver bore 169 and mating bore 167, and ultimately through theworking channel 25. Covering the opening 168 can optimize the aspirationeffect through the working channel.

Returning again to the surgical technique of one embodiment of thepresent invention, once the working channel cannula 20 and the optics 50are in position, as depicted in FIG. 10 step (i) and FIG. 11, theparaspinous tissue can be reflected using instruments as describedabove, and a laminectomy performed using various rongeurs, curettes anddrills. As necessary, the cannula 20 can be angled to allow a greaterregion of bone removal, which may be necessary for access to otherportions of the spinal anatomy. In some instances, access to the spinalcanal and the posterior medial aspects of the disc annulus may requirecutting a portion of the vertebral bone that is greater than the innerdiameter of the working channel 25. Thus, some manipulation of thecannula 20 may be necessary to permit removal of a greater portion ofbone. In other operations, multi-level laminectomies or foramenotomiesmay be necessary. In this instance, these multi-level procedures can beconducted by sequentially inserting the working channel cannula 20through several small cutaneous incisions along the spinal mid-line.Alternatively, several working channel cannulas 20 can be placed at eachof the small cutaneous incisions to perform the multi-level bone removalprocedures.

Again, in accordance with the preferred illustrated surgical technique,an opening is cut into the laminae M of the vertebra V providing directvisual access to the spinal canal. itself. As necessary, tissuesurrounding the spinal nerve root can be removed utilizing microsurgical knives and curettes. Once the spinal nerve root is exposed, aretractor, such as the retractors shown in FIGS. 4-8, can be used togently move and hold the nerve root outside the working space. In oneimportant aspect of the two retractors 70, 100, the portion of theretractor passing through the working channel 25 generally conforms tothe inner surface of the cannula 20 so that the working channel 25 isnot disrupted by the retractor tool. Specifically, the effectivediameter within the working channel 25 is reduced only by the thicknessof the curved plates 84, 114 of the retractors 70, 100. In one specificembodiment, this thickness is about 0.3 mm, so it can be seen that thetissue retractors do not significantly reduce the space available in theworking channel 25 for insertion of other tools and instruments.

With the tissue retractor in place within the working channel 25, bonewithin the spinal canal, such as may occur in a burst fracture, can beremoved with a curette or a high speed drill. Alternatively, thefractured bone may be impacted back into the vertebral body with a boneimpactor. At this point, if the spinal procedure to be performed is theremoval of epidural spinal tumors, the tumors can be resected utilizingvarious micro-surgical instruments. In other procedures, the dura may beopened and the intradural pathology may be approached withmicro-surgical instruments passing through the working channel cannula20. In accordance with the specific illustrated technique, with thenerve root retracted posterior medial disc herniations can be readilyexcised directly at the site of the herniation.

One important feature of the present invention is achieved by the largediameter of the working channel 25 in the cannula 20. This largediameter allows the surgeon or surgeons conducting the surgicalprocedure to introduce a plurality of instruments or tools into theworking space. For example, as described above, a tissue retractor anddiscectomy instruments can be simultaneously extended through theworking channel. In that illustrated embodiment, the discectomyinstruments could include a trephine for boring a hole through the discannulus and a powered tissue cutter for excising the herniated discnucleus. Likewise, the present invention contemplates the simultaneousintroduction of other types of instruments or tools as may be dictatedby the particular surgical procedure to be performed. For example, anappropriately sized curette and a rongeur may be simultaneously extendedthrough the working channel into the working space. Since all operationsbeing conducted in the working space are under direct visualizationthrough the viewing element 50, the surgeon can readily manipulate eachof the instruments to perform tissue removal and bone cuttingoperations, without having to remove one tool and insert the other. Inaddition, since the surgical procedures can be conducted without thenecessity of irrigation fluid, the surgeon has a clear view through theworking space of the target tissue. Furthermore, aspects of theinvention which permit a wide range of motion to the viewing element 50allow the surgeon to clearly visualize the target tissue and clearlyobserve the surgical procedures being conducted in the working space.

The surgeon can capitalize on the same advantages in conducting a widerange of procedures at a wide range of locations in the human body. Forexample, facetectomies could be conducted through the working channel bysimply orienting the working channel cannula 20 over the particularfacet joints. The insertion of vertebral fixation elements can also beaccomplished through the device 10. In this type of procedure, anincision can be made in the skin posterior to the location of thevertebra at which the fixation element is to be implanted. Implementingthe steps shown in FIG. 10, the cannula 20 can be positioned through theincision and tissue directly above the particular location on thevertebra to be instrumented. With the optics extending through theworking channel, an insertion tool holding the vertebral fixationelement can be projected through the cannula 20 and manipulated at thevertebra. In one specific embodiment, the fixation element can be a bonescrew. The working channel 25 has a diameter that is large enough toaccept most bone screws and their associated insertion tools. In manyinstances, the location of the bone screw within the vertebra iscritical, so identification of the position of the cannula 20 over thebony site is necessary. As mentioned above, this position can beverified fluoroscopically or using stereotactic technology.

In many prior procedures, cannulated bone screws are driven into thevertebra along K-wires. The present invention eliminates the need forthe K-wire and for a cannulated screw. The working channel itself caneffectively operate as a positioning guide, once the cannula 20 isproperly oriented with respect to the vertebra. Moreover, the device 10allows insertion of the bone screw into the vertebra to be conductedunder direct vision. The surgeon can then readily verify that the screwis passing into the vertebra properly. This can be particularlyimportant for bone screws being threaded into the pedicle of a vertebra.The working channel cannula 20 can be used to directly insert aself-tapping bone screw into the pedicle, or can accept a variety oftools to prepare a threaded bore within the pedicle to receive a bonescrew.

The device 10 can also be used to prepare a site for fusion of twoadjacent vertebrae, and for implantation of a fusion device or material.For example, in one surgical technique, an incision can be made in theskin posterior to a particular disc space to be fused. The incision canbe made anteriorly, posteriorly or posterior laterally. If the incisionis made anteriorly for anterior insertion of the working channel, it isanticipated that care will be taken to retract tissues, muscle andorgans that may follow the path of the incision to the disc space.However, the device 10 of the present invention allows this tissueretraction to occur under direct vision so that the surgeon can easilyand accurately guide the cannula 20 to the disc space without fear ofinjury to the surrounding tissue. As the tissue beneath the skin issuccessively excised or retracted, the working channel cannula 20 can beprogressively advanced toward the anticipated working space adjacent thevertebral disc. Again under direct vision, the disc space can beprepared for implantation of fusion materials or a fusion device.Typically, this preparation includes preparing an opening in the discannulus, and excising all or part of the disc nucleus through thisopening.

In subsequent steps, a bore is cut through the disc annulus and into theendplates of the adjacent vertebrae. A fusion device, such as a bonedowel, a push-in implant or a threaded implant can then be advancedthrough the working channel of device 10 and into the prepared bore atthe subject disc space. In some instances, the preparatory steps involvepreparing the vertebral endplates by reducing the endplates to bleedingbone. In this instance, some aspiration and irrigation may bebeneficial. All of these procedures can be conducted by tools andinstruments extending through the working channel cannula 20 and underdirect vision from the viewing element 50.

In some instances, graft material is simply placed within the preparedbore. This graft material can also be passed through the working channelcannula 20 into the disc space location. In other procedures, graftmaterial or bone chips are positioned across posterior aspects of thespine. Again, this procedure can be conducted through the workingchannel cannula particularly given the capability of the cannula to bemoved to different angles from a single incision site in the skin.

The present invention provides instruments and techniques for conductinga variety of surgical procedures. In the illustrated embodiments, theseprocedures are conducted on the spine. However, the same devices andtechniques can be used at other places in the body. For example, anappropriately sized working channel device 10 can be used to removelesions in the brain. The present invention has particular value forpercutaneous procedures where minimal invasion into the patient isdesirable and where accurate manipulation of tools and instruments atthe surgical site is required. While the preferred embodimentsillustrated above concern spinal procedures, the present invention andtechniques can be used throughout the body, such as in the cranialcavity, the pituitary regions, the gastro-intestinal tract, etc. Theability to reposition the viewing optics as required to visualize thesurgical site allows for much greater accuracy and control of thesurgical procedure. The present invention allows the use of but a singleentry into the patient which greatly reduces the risk associated withopen surgery or multiple invasions through the patient's skin.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

What is claimed is:
 1. A kit for performing a surgical procedure at alocation in a patient's body, comprising: a series of tissue dilatorshaving successively larger diameters for sequential insertion throughthe skin and tissue of the patient; a cannula sized for insertion overthe largest of said dilators to define a working channel through theskin and tissue of the patient after removal of said dilators, saidcannula having a proximal end and an opposite distal end, a firstlongitudinal axis between said ends and a length along said longitudinalaxis sized so that said distal end is adjacent the location in thepatient's body and said proximal end is outside the patient's body; aviewing element extendable into said cannula, said viewing elementhaving a viewing end positionable adjacent the distal end of saidcannula; and a fixture for movably supporting said viewing element onsaid cannula for positioning said viewing element at selected positionsabout said longitudinal axis of said cannula.
 2. The kit of claim 1,wherein said working channel defines an inner dimension sized tosimultaneously receive a plurality of tools therethrough.
 3. The kit ofclaim 1, wherein said fixture includes: a housing attached to theproximal end of the cannula, said housing defining a working channelopening therethrough in communication with said working channel, saidworking channel opening sized to substantially correspond to said innerdimension of said working channel to receive a tool therethrough; saidhousing further defining an optics bore adjacent said working channelopening.
 4. The kit of claim 3, wherein said viewing element includes animage transmission channel extending between said proximal end and saidviewing end.
 5. The kit of claim 4, wherein said viewing elementincludes a fiber-optic cable having illumination fibers and imagetransmission fibers.
 6. The kit of claim 4, wherein said viewing elementincludes a lens, said lens defines an optical axis, said optical axisbeing offset at an angle relative to a longitudinal axis of said opticsbore.
 7. The kit of claim 1, wherein said fixture includes a housingdefining a working channel opening in communication with said workingchannel of said cannula and an optics bore for receiving said viewingelement therethrough in communication with said working channel, saidoptics bore having a second longitudinal axis substantially parallel tosaid first longitudinal axis, said housing being rotatable relative tosaid cannula so that said second longitudinal axis of said optics borerotates about said first longitudinal axis of said working channel. 8.The kit of claim 7, wherein said optics bore is defined by a C-shapedclip.
 9. The kit of claim 8, wherein said C-shaped clip is formed of aresilient material and said optics bore defined by said clip has aninner dimension that is slightly less than an outer dimension of saidviewing element so that said viewing element resiliently deflects saidC-shaped clip when said viewing device is disposed within said opticsbore.
 10. The kit of claim 7, wherein said housing further defines anumber of grooves in said receiving bore.
 11. The kit of claim 10,further comprising sealing members disposed in each of said number ofgrooves, said sealing members disposed between said housing and saidouter dimension of said cannula.
 12. The kit of claim 7 wherein saidfixture includes engagement means, disposed between said housing andsaid cannula when said fixture is mounted to said proximal end of saidcannula for providing a gripping engagement between said housing andsaid cannula.
 13. The kit of claim 1, wherein said cannula iscylindrical.
 14. The kit of claim 1, wherein at least one of said tissuedilators includes a sleeve having a tapered working end and an oppositeend, said working end configured to displace tissue.
 15. The kit ofclaim 14, wherein said at least one tissue dilator further comprises agripping portion on an outer surface of said sleeve adjacent saidopposite end, said gripping portion defining a plurality ofcircumferential grooves configured for manually gripping the dilator tomanipulate the dilator within tissue.
 16. A kit for performing asurgical procedure at a location in a patient's body, comprising: aseries of tissue dilators having successively larger diameters forsequential insertion through the skin and tissue of the patient; acannula sized for insertion over the largest of said dilators to definea working channel through the skin and tissue of the patient afterremoval of said dilators, said cannula having a proximal end and anopposite distal end, a first longitudinal axis between said ends and alength along said longitudinal axis sized so that said distal end isadjacent the location in the patient's body and said proximal end isoutside the patient's body; a viewing element sized for introductioninto said cannula; and a support connected to said viewing element andmounted at one end of said cannula to permit positioning of said viewingelement relative to said cannula at selected arcuate locations aboutsaid longitudinal axis of said cannula.
 17. The kit of claim 16, whereinsaid support includes a fixture movably mounted to said cannula at saidproximal end, said fixture defining an optics bore sized to receive atleast a portion of said viewing element therethrough.
 18. The kit ofclaim 17, wherein: said viewing element is elongated having a lens at adistal end and an opposite proximal end; and said elongated viewingelement being slidably disposed within said optics bore to extend orretract said lens relative to said distal end of said cannula.
 19. Thekit of claim 17, wherein said fixture is configured to engage saidcannula at said proximal end to support said viewing element forrotation about said longitudinal axis of said cannula.
 20. A kit forperforming a surgical procedure at a location in a patient's body,comprising: a series of tissue dilators having successively largerdiameters for sequential insertion through the skin and tissue of thepatient; an elongated cannula having an inner dimension for insertionover the largest of said dilators to define a working channel throughthe skin and tissue of the patient after removal of said dilators and anouter dimension sized for percutaneous introduction into a patient, saidcannula further including a distal working end and an opposite proximalend, said working channel sized for receiving at least one tooltherethrough; a viewing element having a first end connectable to aviewing apparatus and a lens disposed at an opposite second end; andmeans for movably supporting said viewing element within said workingchannel to permit movement of said lens at said working end withoutmovement of the at least one tool when the at least one tool extendsthrough said working channel.
 21. The kit of claim 20, wherein saidmeans for movably supporting includes a fixture mounted adjacent saidproximal end of said cannula and defining a working channel openingcommunicating with said working channel and sized to receive the atleast one tool therethrough.
 22. The kit of claim 21, wherein saidfixture is rotatably mounted to said cannula to permit arcuate movementof said viewing element.
 23. A kit for performing a surgical procedureat a location in a patient's body, comprising: a series of tissuedilators having successively larger diameters for sequential insertionthrough the skin and tissue of the patient; an elongated cannula sizedfor insertion over the largest of said dilators to define a workingchannel through the skin and tissue of the patient after removal of saiddilators, said cannula having a length and defining a first area withinsaid cannula transverse to said length and an outer dimension sized forpercutaneous introduction into a patient, said cannula further includinga distal working end and an opposite proximal end, said working channelextending between said ends having a second area sized for receiving asurgical tool therethrough; a viewing element including a lens at adistal end thereof; and a fixture supporting said viewing elementadjacent said working channel with said lens disposed adjacent saidworking end of said cannula, whereby said second area is substantiallyequal to said first area.
 24. The kit of claim 23, wherein said secondarea is sized to simultaneously receive a plurality of surgical toolstherethrough.
 25. The kit of claim 24, wherein said viewing element hasa proximal end adjacent said proximal end of said cannula and includesan image transmission channel extending from said lens at least to saidproximal end thereof.
 26. The kit of claim 25, wherein said viewingelement includes a fiber-optic cable having illumination fibers andimage transmission fibers disposed within said image transmissionchannel.
 27. The kit of claim 23, wherein said fixture includes meansfor removably mounting said fixture to said cannula adjacent saidproximal end of said cannula.
 28. The kit of claim 27, wherein saidfixture includes means for supporting said viewing element within saidworking channel.
 29. The kit of claim 23, wherein at least one of saidtissue dilators includes a sleeve having a tapered working end and anopposite end, said working end configured to displace tissue.
 30. Thekit of claim 29, wherein said at least one tissue dilator furthercomprises a gripping portion on an outer surface of said sleeve adjacentsaid opposite end, said gripping portion defining a plurality ofcircumferential grooves configured for manually gripping the dilator tomanipulate the dilator within tissue.